Core-shell resin pellet having melt viscosity difference between the core resin and the shell resin

ABSTRACT

Provided are a resin blend for melt processing, a pellet and a method of preparing a resin article using the same. The resin blend may include a first resin, and a second resin having a difference in melt viscosity from the first resin of 0.1 to 3000 pa*s at a shear rate of 100 to 1000 s −1  and a processing temperature of the resin blend. The resin blend can improve mechanical and surface characteristics of a resin article. Further, since coating or plating is not required for manufacturing a resin article, a manufacturing time and/or cost can be reduced, and productivity can be increased.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of International ApplicationPCT/KR2011/003885, with an international filing date of May 26, 2011,which claims priority to and the benefit of Korean Patent ApplicationNo. 2010-0050639, filed May 28, 2010, Korean Patent Application No.2010-0081084, filed Aug. 20, 2010, and Korean Patent Application No.2011-0033146, filed Apr. 11, 2011, the disclosures of which areincorporated herein by reference in their entireties.

BACKGROUND

Plastic resins have various applications including automobile parts,helmets, parts of electric devices, parts of textile spinning machines,toys or pipes because of their easy processability and excellentproperties such as tensile strength, modulus of elasticity, heatresistance and impact resistance.

Particularly, home appliance functions as home interior accessories aswell as its own function as home appliance and parts of automobiles andtoys are in direct contact with a human body, these products arerequired to be environment-friendly and to have excellent scratchresistance. However, plastic resins are generally decomposed by oxygenin the air, ozone and light and easily changed in color when exposed toan external environment for over a certain period of time. As a result,plastic resins suffer from decrease of weather resistance and strength,which makes them to be easily broken. Thus, an additional coating orplating process has been usually applied to plastic resins to improvethese problems and surface properties. However, such a coating orplating process can drop efficiency and economic feasibility of amanufacturing process of plastic resins or generate large amount oftoxic materials during the process or disposal of a product.

Accordingly, various methods have been suggested to improve propertiesof plastic resins such as scratch resistance, heat resistance andweather resistance without using an additional coating or platingprocess. For example, a method of adding inorganic particles to highmolecule resins has been suggested to improve physical properties suchas abrasion resistance and stiffness of the resins. However, this methodmay deteriorate the processability of plastic resins and impact strengthand gloss due to the addition of inorganic particles.

SUMMARY OF THE INVENTION

The present invention provides a resin blend for melt processing. Theresin blend can improve mechanical and surface characteristics of theresin article by enabling formation of a surface layer on the resinarticle through a layer separation. Further, since a step for separatecoating or plating is not required for manufacturing the resin article,a manufacturing time and/or manufacturing cost can be reduced, andproductivity can be increased.

The present invention further provides a pellet produced by using theresin blend and a method for preparing the pellet.

The present invention still further provides a method of preparing aresin article by using the resin blend or the pellet.

In one embodiment, a resin blend includes a first resin and a secondresin having a difference in melt viscosity from the first resin of 0.1to 3000 pa*s at a shear rate of 100 to 1000 s⁻¹ and at a processingtemperature of the resin blend.

In another embodiment, a pellet includes a core including a first resinand a shell including a second resin having a difference in meltviscosity from the first resin of 0.1 to 3000 pa*s at a shear rate of100 to 1000 s⁻¹ and at a processing temperature of the resin blend.

In another embodiment, a method of preparing a resin article includesmelting a blend of a first and second resin to form a melt blend andprocessing the melt blend to form the resin article. A melt viscositydifference between the first resin and the second resin is 0.1 to 3000pa*s at a shear rate of 100 to 1000 s⁻¹ and a processing temperature ofthe blend.

In another embodiment, a method of preparing a resin article includesmelting a pellet including a core including a first resin and a shellincluding a second resin to form a melt, and processing the melt to formthe resin article. A melt viscosity difference between the first resinand the second resin is 0.1 to 3000 pa*s at a shear rate of 100 to 1000s⁻¹ and a processing temperature of the blend.

In another embodiment, a resin blend for forming a layer-separatedstructure includes a first resin and a second resin having a lower meltviscosity than the first resin. The second resin is disposed between thefirst resin and an ambient air in response to a melting process.

In another embodiment, a resin blend for forming a layer-separatedstructure includes a base resin and a functional resin. A value of amelt viscosity of the functional resin is different from that of thebase resin, and the value of the value viscosity of the functional resinis dependent on the properties of the base resin.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become more apparent to those of ordinary skill in theart by describing in detail exemplary embodiments thereof with referenceto the attached drawings, in which:

FIG. 1 is an illustrative schematic diagram showing a resin blend,according to one embodiment of the present invention.

FIG. 2 is an illustrative schematic diagram showing a resin blend,according to another embodiment of the present invention.

FIG. 3 is an illustrative schematic diagram showing a resin articleformed by using a resin blend including a first resin and a secondresin, according to one embodiment of the present invention.

FIG. 4 is an illustrative schematic diagram showing a resin articleformed by using a resin blend including a first resin, a second resinand a third resin, according to another embodiment of the presentinvention.

FIG. 5 is an illustrative schematic diagram showing a resin article,according to another embodiment of the present invention.

FIG. 6 is an illustrative schematic diagram showing a pellet having acore and a shell.

FIG. 7 is a SEM image illustrating a cross-sectional view of a resinarticle prepared according to Example 1.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, a resin blend for preparing a resin article having asurface layer formed as a result of a layer separation without aseparate coating or plating process, a pellet and a method of preparinga resin article using the same according to embodiments of the presentinvention will be described in detail.

A “blend” may be a mixture of two or more different species of resins. Atype of blend may include, but is not limited, a mixture of two or moreresins in one matrix, or a mixture of two or more kinds of pellets.Particularly, the mixture of two or more resins in one matrix may be apellet containing a mixture of two or more resins. For example, amixture of a first resin and a second resin can be contained in a singlepellet. Alternatively, in the mixture of two or more kinds of pelletseach kind of pellet contains one kind of resin. For example, a blend caninclude a mixture of a pellet containing a first resin and a pelletcontaining a second resin

A “melting process” or “melt processing” may refer to a process ofmelting the resin blend at not less than a melting temperature (Tm) ofthe resin blend to form a melt blend and forming a desired product byusing the melt blend. For example, the melting process or melt processmay include injection molding, extrusion, blow molding, expandingmolding and the like.

A “layer separation” may indicate that a portion of a resin blend thatis separated from the remaining resin blend by phase-separation, forms alayer that is visibly separated from a layer of the remaining resinblend. For example, the separated portion of the resin blend can be richwith or contain a substantial amount of a second resin and the remainingresin blend can be rich with or contain a substantial amount of a firstresin. The layer separation results in a layer-separated structure in aresin article or a pellet, which is distinguished from a sea-islandstructure where the phase-separated portion is partially distributed inthe entire resin blend. The layer separation of the resin blend resultsin two or more separate layers, preferably two separate layers formed ina resin article or a pellet prepared by the resin blend.

The present inventors confirmed through experimentation that a layerseparation occurs when a resin blend comprising a first resin and asecond resin having certain physical properties different from the firstresin is used, and that such a layer separation enables to obtainsubstantially the same effects as applying a coating on a surface ofpellets or resin articles without using additional process during orafter melting process or melt processing such as extrusion or injection.Such a layer separation occurs during the melting process or meltprocessing and the second resin forms a surface layer on the pellets orthe resin articles.

Thus, the resin blend for a melting process or melt processing accordingto one embodiment of the present invention may provide a resin articlehaving improved mechanical and surface characteristics without the needof an additional processing such as coating or plating. In the past, asolvent with lower viscosity was used to remove a resin article easilyfrom a mold. When the resin blend is used, a molecular weightdistribution of a second resin and a difference in physical propertiesbetween a first resin and the second resin may cause the layerseparation, which improves surface and mechanical properties of a resinarticle. For example, the resin blend of the present invention may belayer-separated by a melting process to form a resin article having aspecific function on a surface of the resin article, without anadditional process, such as coating and plating.

As such, the layer separation may be attributed to a difference inphysical properties between first and second resins and/or a molecularweight distribution of the second resin. Here, the different physicalproperties may, for example, include surface energy, melt viscosity,glass transition temperature and a solubility parameter and the like.Although it is illustrated here that two resins are blended for thepurpose of explanation of the present invention, it will be apparent toone of skilled in the art that three or more resins having differentphysical properties may be blended and separated during a meltingprocess.

In one embodiment, a resin blend for a melt processing includes a firstresin and a second resin having a difference in melt viscosity from thefirst resin of 0.1 to 3000 pa*s at a shear rate of 100 to 1000 s⁻¹ andat a processing temperature of the resin blend.

The difference in a melt viscosity between the first resin and thesecond resin may be 0.1 to 3000 pa*s, 1 to 2000 pa*s, or 1 to 1000 pa*sat a shear rate of 100 to 1000 s⁻¹ and at a processing temperature ofthe resin blend. The difference in a melt viscosity between the firstresin and the second resin can also be 100 to 500 pa*s, 500 to 3000pa*s, 1500 to 3000 pa*s, or 500 to 2500 pa*s at a shear rate of 100 to1000 s⁻¹ and at a processing temperature of the resin blend. It will beapparent to one of skilled in the art that the listed ranges are onlyexamples for the purpose of description of the present invention and anyvalue within the range of 0.1 to 3000 pa*s at the above shear rate andat a processing temperature of the resin blend can be selected. When thedifference in the melt viscosity is too low for example less than 0.1pa*s at the shear rate and at a processing temperature of the resinblend, the layer separation of the melt-processed resin blend does noteasily occur because the first and second resins are too easily mixedtogether. When the difference in the melt viscosity is too high forexample greater than 3000 pa*s at the shear rate and at a processingtemperature of the resin blend, the first and second resins may not beattached to each other due to a high difference of the melt viscosityand thus may be detached.

The lower and/or upper limits of the difference in melt viscosity may beany numeric value of 0.1 to 3000 pa*s, and be dependent on theproperties of the first resin. Particularly, when a first resin is usedas a base resin and a second resin is used as functional resin toimprove surface properties of the first resin, the second resin may bechosen such that a difference in a melt viscosity between the first andsecond resins is 0.1 to 3000 pa*s at a shear rate of 100 to 1000 s⁻¹ andat a processing temperature of the resin blend. Since a value of themelt viscosity of the second resin (e.g., functional resin) may bedifferent based on the properties of the first resin (e.g., base resin),the difference in the melt viscosity may be determined based on theproperties of the first resin. The properties of the first resin mayinclude, but is not limited to, a kind of the first resin, or a value ofthe melt viscosity of the first resin. In one embodiment, the differencein melt viscosity may be selected by considering fluidity of the secondresin in a melt-processed blend of the first and second resins.

By way of an example, in the case that the resin blend of the first andsecond resins having the difference in melt viscosity of 0.1 to 3000pa*s at a shear rate of 100 to 1000 s⁻¹ and at a processing temperatureof the resin blend is used, when the resin blend of the first and secondresins is melt-processed, the melt-processed resin blend is exposed toan ambient air. In the melt-processed resin blend, the first and secondresins can be separated due to the difference of fluidity between thefirst resin and second resin. Particularly, the second resin having asmaller melt viscosity compared to the first resin may have a higherfluidity than the first resin, and move to a surface that contacts theambient air. Thus, the second resin may be positioned adjacent to anambient air to form a second resin layer as a surface layer. A firstresin layer may be positioned on an inner side of the second layer.Accordingly, a layer separation can occur between the first and secondresins of the resin blend.

The melt viscosity may be measured using a capillary flow meter, andindicates a shear viscosity (pa*s) at a predetermined processingtemperature and shear rate (/s). The shear rate is a shear rate appliedwhen the resin blend is processed, and may be selected depending on aprocessing method, for example, shear rate of 100 to 1000 s⁻¹. It willbe apparent to one of skilled in the art to control the shear rateaccording to the processing method.

The processing temperature is a temperature at which the resin blend isprocessed. For example, when the resin blend is subject to a meltprocessing such as extrusion or injection, the processing temperature isa temperature at which the melt processing such as extrusion orinjection is performed. The processing temperature may be controlledaccording to a resin subjected to melting processes such as extrusion orinjection. It will be apparent to one of skilled in the art to controlthe processing temperature according to the kinds of resins of the resinblend. For example, a temperature for extruding or injecting a resinblend including a first a an ABS resin as a first resin and a secondresin obtained by polymerizing a methyl methacrylate-based monomer maybe 210 to 240° C.

The resin blend may be separated into two or more layers. The resinblend including the first resin and the second resin may belayer-separated into three layers, i.e., Second resin layer/First resinlayer/Second resin layer, as shown in FIG. 3, when two opposite sides ofthe melt-processed resin blend are exposed to the ambient air.Alternatively, when only one side of the melt-processed resin blend isexposed to the ambient air, the resin blend may be layer-separated intotwo layers, i.e., Second resin layer/First resin layer. Further, when aresin blend including a first resin, a second resin and a third resin ismelt-processed, the melt-processed resin blend may be layer-separatedinto five layers, i.e., Third resin layer/Second resin layer/First resinlayer/Second resin layer/Third resin layer, as shown in FIG. 4, by usingthe differences in physical properties, for example, surface energy,melt viscosity or solubility parameter, among the three resins.Furthermore, when all sides of the melt-processed resin blend areexposed to the ambient air, the resin blend may be layer-separated intoall direction to form a core-shell structure, as shown FIG. 5.

In another embodiment, a resin blend for melt processing comprises afirst resin and a second resin having a difference in surface energyfrom the first resin at 25° C. of 0.1 to 35 mN/m.

The difference in surface energy between the first and second resins at25° C. may be 0.1 to 35 mN/m, 1 to 30 mN/m, or 1 to 20 mN/m. Thedifference in surface energy between the first and second resins at 25°C. can also be 1 to 10 mN/m, 0.5 to 10 mN/m, 5 to 35, 15 to 35 mN/m or 5to 30 mN/m. It will be apparent to one of skilled in the art that thelisted ranges are only examples for the purpose of the description ofthe present invention and any values within 0.1 to 35 mN/m can bechosen. By way of an example, in the case that the resin blend of thefirst and second resins is melt-processed such as extrusion orinjection, the melt-processed resin blend is exposed to an ambient air.In the melt-processed resin blend, the first and second resins can beseparated due to the higher affinity of the second resin to the ambientair compared to the fist resin. Particularly, the second resin having asmaller surface energy compared to the first resin may have ahydrophobic property, and due to its fluidity in the melt-processedresin blend, move to surface that contacts the ambient air. Thus, thesecond resin may be positioned adjacent to an ambient air to form asecond resin layer as a surface layer. A first resin layer may bepositioned on an inner side of the second layer. Accordingly, a layerseparation can occur between the first and second resins of the resinblend. When the difference in surface energy is too low such as lessthan 0.1 mN/m, the layer separation of the melt-processed resin blenddoes not easily occur and the second resin in a mixture of melting statecan be difficult to be positioned on the surface by moving through thematrix of the resin blend. When the difference in surface energy is toohigh such as greater than 35 mN/m, the first and second resins may notbe attached to each other due to a high difference of surface energy,and thus may be detached.

The lower and/or upper limits of the difference in surface energy may beany numeric value of 0.1 to 35 mN/m, and be dependent on the propertiesof the first resin. Particularly, when a first resin is used as a baseresin and a second resin is used a functional resin to improve surfaceproperties of a first resin, the second resin may be selected such thata difference in surface energy between the first and second resins is0.1 to 35 mN/m at 25° C. Since a value of the surface energy of thesecond resin (e.g., functional resin) may be different based on theproperties of the first resin (e.g., base resin), the difference insurface energy may be determined based on the properties of the firstresin. The properties of the first resin may include, but is not limitedto, a kind of the first resin, or a value of the surface energy of thefirst resin. In one embodiment, the difference in surface energy may beselected by considering hydrophobicity of the second resin in a meltingmixture of the first and second resins.

In still another embodiment, a resin blend for a melt processingincludes a first resin and a second resin having a difference insolubility parameter from the first resin at 25° C. of 0.001 to 10(J/cm³)^(1/2).

The difference in a solubility parameter between the first resin and thesecond resin at 25° C. may be 0.001 to 10 (J/cm³)^(1/2), 0.01 to 5(J/cm³)^(1/2), or 0.01 to 3 (J/cm³)^(1/2). The difference in asolubility parameter between the first resin and the second resin at 25°C. can also be 0.01 to 2 (J/cm³)^(1/2), 0.1 to 1 (J/cm³)^(1/2), 0.1 to10 (J/cm³)^(1/2), 3 to 10 (J/cm³)^(1/2), 5 to 10 (J/cm³)^(1/2), or 3 to8 (J/cm³)^(1/2). The lower and/or upper limit of the difference insolubility parameter may be any numeric value of 0.001 to 10(J/cm³)^(1/2), and be dependent on a solubility parameter of the firstresin. It will be apparent to one of skilled in the art that the listedvalues are only examples for the purpose of description of the presentinvention and any value within the range of 0.001 to 10 (J/cm³)^(1/2) at25° C. can be chosen. A solubility parameter is an intrinsic property ofresin reflecting solubility depending on a polarity of each resinmolecule, and the solubility parameter for each resin is generallyknown. When the difference in the solubility parameter is too small, forexample, less than 0.001 (J/cm³)^(1/2), the layer separation does noteasily occur because the first and second resins are too easily mixedtogether. When the difference in the solubility parameter is too big,for example, greater than 10 (J/cm³)^(1/2), the first and second resinsmay not be attached to each other due to a high difference of solubilityparameter, and thus may be detached.

The lower and/or upper limits of the difference in solubility parametermay be any numeric value of 0.001 to 10 (J/cm³)^(1/2), and be dependenton the properties of the first resin. Particularly, when a first andsecond resins are used as a base and functional resins, respectively,the second resin may be chosen such that a difference in a solubilityparameter between the first and second resins is 0.001 to 10(J/cm³)^(1/2) at 25° C. Since a value of the solubility parameter of thesecond resin (e.g., functional resin) may be different based onproperties of the first resin (e.g., base resin), the difference in thesolubility parameter may be determined based on the properties of thefirst resin. The properties of the first resin may include, but is notlimited to, a kind of the first resin, or a value of the solubilityparameter of the first resin. In one embodiment, the difference insolubility parameter may be selected by considering immiscibilitybetween the first resin and the second resin in a melting mixture of thefirst and second resins.

By way of an example, in the case that the resin blend of the first andsecond resins having the difference in solubility parameter of 0.001 to10 (J/cm³)^(1/2) at 25° C. is used, when the resin blend of the firstand second resins is melt-processed, the melt-processed resin blend isexposed to an ambient air, the first and second resins can be separateddue to the degree of immiscibility between the first resin and secondresin. Particularly, the second resin having a difference in solubilityparameter from the first resin at 25° C. of 0.001 to 10 (J/cm³)^(1/2)may be immiscible with the first resin. Thus, the second resin havingadditionally lower surface tension or lower melt viscosity than that ofthe first resin may move and be positioned adjacent to an ambient air toform a second resin layer. A first resin layer may be positioned on aninner side of the second layer. Accordingly, a layer separation can beoccurred between the first and second resins of the resin blend.

In still another embodiment, a molecular weight distribution (PDI) ofthe second resin is 1 to 2.5 or 1 to 2.3. The molecular weightdistribution can also be 1 to 2, 1.3 to 2.5, 1.5 to 2.5, or 1.3 to 2.3.The lower and/or upper limits of the molecular weight distribution (PDI)of the second resin may be any numeric value of 1 to 2.5. It will beapparent to one of skilled in the art that the listed ranges are onlyexamples for the purpose of the description of the present invention andany value within the range of 1 to 2.5 can be selected. When themolecular weight distribution of the second resin is greater than 2.5,the first resin is easily mixed with the second resin due to the lowmolecular weight portion of the second resin, or the mobility of thesecond resin in a mixture of melting state is degraded due to the highmolecular weight portion thereof, and thus the layer separation betweenthe first resin and the second resin does not easily occur.

In still another embodiment, a weight average molecular weight (Mw) ofthe second resin of the resin blend is 30,000 to 200,000, or 50,000 to150,000. The weight average molecular weight (Mw) of the second resin ofthe resin blend can also be 50,000 to 200,000, 80,000 to 200,000, 80,000to 150,000, 50,000 to 120,000, or 80,000 to 120,000. The lower and/orupper limits of the weight average molecular weight (Mw) of the secondresin may be any numeric value of 30,000 to 200,000. It will be apparentto one of skilled in the art that the listed ranges are only examplesfor the purpose of the description of the invention and any value withinthe range of 30,000 to 200,000 can be chosen. When the weight averagemolecular weight is smaller than 30,000, the first resin is easily mixedwith the second resin, and when the weight average molecular weight isgreater than 200,000, the mobility of the second resin in a mixture ofmelting state is degraded and thus the layer separation between thefirst and second resin does not easily occur.

Meanwhile, the first resin may determine the physical properties of aresin article and may be selected according to a kind of the desiredresin article and processing conditions. As the first resin, anysynthetic resin may be used without limitation, but may preferablyinclude a styrene-based resin such as an acrylonitrile butadiene styrene(ABS)-based resin, a polystyrene-based resin, an acrylonitrile styreneacrylate (ASA)-based resin or a styrene-butadiene-styrene blockcopolymer-based resin; a polyolefin-based resin such as a high densitypolyethylene-based resin, a low density polyethylene-based resin or apolypropylene-based resin; a thermoplastic elastomer such as anester-based thermoplastic elastomer or olefin-based thermoplasticelastomer; a polyoxyalkylene-based resin such as apolyoxymethylene-based resin or a polyoxyethylene-based resin; apolyester-based resin such as a polyethylene terephthalate-based resinor a polybutylene terephthalate-based resin; a polyvinylchloride-basedresin; a polycarbonate-based resin; a polyphenylenesulfide-based resin;a vinyl alcohol-based resin; a polyamide-based resin; an acrylate-basedresin; engineering plastics; or a copolymer or mixture thereof.

The engineering plastics are a group of plastics that exhibit superiormechanical and thermal properties. By way of examples, polyetherketone,polysulphone, polyimides and the like may be used as the engineeringplastics.

The second resin shows the difference in physical properties from thefirst resin as described above, and may be chosen to provide specificfunctions to a surface of a resin article. The functions of the secondresins are not particularly limited. For example, the second resins maybe resins providing a high surface hardness function, an anti-wearfunction, an anti-contamination function, an anti-fingerprint function,a color, a pearling function, a high-gloss function, a non-glossfunction, a barrier function or a combination thereof.

The second resin may have either or all of a thermal curable functionalgroup and a radiation, such as UV, curable functional group withoutspecific limitation. When a thermal curable functional group is includedin the second resin, the layer separation occurs and hardness may beincreased due to the crosslinks formed in melt processing such asextrusion or injection.

As another examples of the second resin, a (meth)acrylate-based resin,an epoxy-based resin, an oxetane-based resin, an isocyanate-based resin,a silicon-based resin, a fluorine-based resin, or a copolymer or mixturethereof may be included.

The (meth)acrylate-based resin is a resin formed by polymerizing anacryl or methacryl monomer as a main component, which may include, butis not limited to, alkyl methacrylates such as methyl methacrylate,ethyl methacrylate, propyl methacrylate, butyl methacrylate, cyclohexylmethacrylate, octyl methacrylate, lauryl methacrylate or stearylmethacrylate; alkyl acrylates such as methyl acrylate, ethyl acrylate,propyl acrylate, butyl acrylate, octyl acrylate, lauryl acrylate orstearyl acrylate; or glycidyl (meth)acrylates such as glycidylmethacrylate or glycidyl acrylate.

The epoxy-based resin is a resin containing an epoxy group, and may be,but is not limited to, a bisphenol type such as bisphenol A, bisphenolF, bisphenol S or a hydro additive thereof; a novolac type such asphenol novolac or cresol novolac; a nitrogen-containing ring type suchas triglycidyl isocyanurate or hydantoin; an alicyclic type; analiphatic type; an aromatic type such as naphthalene or biphenyl; aglycidyl type such as glycidyl ether, glycidyl amine or glycidyl ester;a dicyclo type such as dicyclopentadiene; an ester type; or an etherester type.

The oxetane-based resin is a resin formed by polymerizing an oxetanemonomer having at least one oxetane ring, and may be, but is not limitedto, 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene,di[1-ethyl(3-oxetanyl)]methylether, or a polyoxetane compound such asphenol novolac oxetane, terephthalate bisoxetane or biphenylenebisoxetane.

The isocyanate-based resin is a resin containing an isocyanate group,and may be, but is not limited to, diphenylmethane diisocyanate (MDI),toluene diisocyanate (TDI) or isophorone diisocyanate (IPDI).

The silicon-based resin is a resin containing a main chain connected bya siloxane bond which is a silicon-oxygen bond, and may be, but is notlimited to, polydimethylsiloxane (PDMS).

The fluorine-based resin is a resin containing a fluorine atom, and maybe, but is not limited to, polytetrafluoroethylene (PTFE),polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), orpolyvinylfluoride (PVF).

The resin blend may include the second resin in an amount of 0.1 to 50parts by weight, or 1 to 20 parts by weight, based on 100 parts byweight of the first resin. The amount of second resin may also be 0.1 to35 parts by weight, 0.1 to 20 parts by weight, 5 to 50 parts by weight,10 to 50 parts by weight, 5 to 35 parts by weight or 5 to 20 parts byweight, based on 100 parts by weight of the first resin. The lowerand/or upper limits of the amount of the second resin included in theresin blend, may be any numeric value of 0.1 to 50 parts by weight basedon 100 parts by weight of the first resin. It will be apparent to one ofskilled in the art that the listed ranges are only examples for thepurpose of the description of the present invention and any value withinthe range of 0.1 to 50 parts by weight can be chosen. When the secondresin is included in an amount smaller than 0.1 parts by weight based on100 parts by weight of the first resin, the layer separation does notoccur. When the second resin is included in an amount greater than 50parts by weight, the manufacturing cost increases due to the high costof the second resin.

In another embodiment, a resin blend for forming a layer-separatedstructure includes a base resin and a functional resin. A value of amelt viscosity of the functional resin is different from that of thebase resin, and the value of the melt viscosity of the functional resinis dependent on properties of the base resin.

The base resin, for example, a first resin, may substantially determinethe physical properties of a resin article. The functional resin, forexample, a second resin, may provide specific functions to a surface ofa resin article. The properties of the base resin and the specificfunctions of the second resin are the same as described the above.

The present invention further provides a pellet prepared using the resinblend described above. The pellet may have a core having a first resinand a shell having a second resin formed on a surface of the pellet bylayer separation. The first resin is disposed in the middle thereof(core), and a second resin is layer-separated from the first resin anddisposed to surround the first resin and to form a shell of the pellet.The structure of a pellet can be illustrated as shown in FIG. 6.

The first resin and the second resin have different properties asdescribed above. For example, the first resin and the second resin mayhave a difference in surface energy from the first resin at 25° C. of0.1 to 35 mN/m; a difference in melt viscosity of 0.1 to 3000 pa*s at ashear rate of 100 to 1000 s⁻¹ and at a processing temperature of thepellet; or a difference in solubility parameter of 0.001 to 10.0(J/cm³)^(1/2) at 25° C. Further, the second resin may have a molecularweight distribution (PDI) of 1 to 2.5 or a weight average molecularweight (Mw) of 30,000 to 200,000. The first and second resins havealready been described in detail, and thus further detailed descriptionwill be omitted.

The present invention still further provides a method of preparing aresin article comprising a melt processing of the resin blend asdescribed above. The resin article prepared has a layer-separatedstructure. In one embodiment, the method includes melting a blend offirst and second resins to form a melt blend and processing the meltblend to prepare a resin article and the melt viscosity differencebetween the first resin and the second resin is 0.1 to 3000 pa*s at ashear rate of 100 to 1000 s⁻¹ and at a processing temperature of theblend.

As described above, since the second resin has a different physicalproperty from the first resin such as higher hydrophobicity, the layerseparation may occur during the melt processing such as injection orextrusion of the resin blend. This layer separation enables a layer ofthe second resin to be formed on a surface of pellets or a resin articlewithout the need of additional process and thus provides the sameresults as applying a coating on a surface of pellets or a resin articleby a separate step. Further, since the second resin can be formed tohave a function such as gloss or anti-contamination and can be separatedfrom the first resin during the melt processing of the resin blend, theresin article in which the first resin constitutes a body and the secondresin forms a surface on the body can be easily manufactured withoutperforming additional process. Still further, when the first and secondresins are used to form a pellet, the pellet having a core of the firstresin and a shell of the second resin can be manufactured by the meltprocessing of the resin blend without performing any additional process.Furthermore, The melt processing may be performed under a shear stress,and may include, but is not limited to, injection and extrusion.

In one embodiment, the resin blend may be prepared to include a firstresin and a second resin that have a difference in physical properties,for example, surface energy, melt viscosity or solubility parameter. Theresin blend may be melted to form a melt blend and the melt blend may befurther processed to form pellets or a resin article. For example, themelted resin blend may be subject to an extrusion process to prepare apellet. As described above, the first and second resins may be separatedduring the melt processing such as extrusion. Particularly, the secondresin may move to contact with an ambient air due to its hydrophobicproperty compared to the first resin. A second resin layer may bepositioned adjacent to an ambient air, and a layer substantially formedof a first resin layer may be positioned on an inner side of the secondresin layer. Accordingly, the resin article may have a body that isformed of the first resin and a surface that is on the body and isformed of the second resin. Further, by the above described process, thepellet may have structure in which the first resin is disposed in themiddle of the pellet and the second resin is disposed to surround thefirst resin.

In another embodiment, the pellet may be further processed, for exampleinjection, to form a resin article. For example, the pellet having firstand second resins of different physical properties may be melted andfurther processed, for example, injected, to form a final product, forexample, a resin article. As described above, due to the difference invarious physical properties, for example, surface energy, melt viscosityor solubility parameter, of the first and second resins of the pellets,the resin article formed of the pellets may have separated layers, i.e.,a body formed of the first resin and a surface layer formed of thesecond resin and placed on the body. Although it is illustrated that thepellets of core-shell structure having the first and second resins aremelt-processed to form a resin article for the purpose of explanation,it will be apparent to one of skilled in the art that a mixture of twoor more pellets or pellets including the composition of two or moreresins may be used to form a resin article. Alternatively, the resinblend may be directly prepared into a resin article through the meltprocessing such as injection, as described above. The processingtemperature to be applied may be changed depend on kinds of the firstand second resins used in the melt processing of the resin blend.

In some embodiments, the method of preparing a resin article may furtherinclude curing a product having a layer-separated structure (forexample, a resin article having a body and a surface layer on the body)obtained from the melt processing of the resin blend. For example, afteran extrusion or injection, thermal curing and/or radiation curing, suchas UV curing, may be further performed on the melt-processed product.When necessary, chemical or physical treatment, such as a heattreatment, may be performed after the process.

Meanwhile, the method of preparing a resin article may further includepreparing a second resin before the melt processing of the resin blend.The second resin may be selected depending on a first resin, asdescribed above. For example, the second resin may be selected such thata value of a melt viscosity of the second resin is less than that of thefirst resin. Further, the second resin may be selected to add specificfunctions on a surface of the resin article. As examples for thepreparation of the second resin, there is bulk polymerization, solutionpolymerization, suspension polymerization, or emulsion polymerization.

In the suspension polymerization method, the second resin may beprepared by dispersing a monomer in a reaction medium, adding andblending an additive such as a chain transfer agent, an initiator and adispersion stabilizer in the reaction solvent and polymerizing the blendat 40° C. or higher. One of skilled in the art can easily select thekind of monomer based on a desired function such as an abrasionresistance function, an anti-wear function, an anti-contaminationfunction, an anti-fingerprint function, a colored function, a pearlfunction, a high-gloss function, a non-gloss function and a barrierfunction. By way of examples of the monomer, there are (meth)acrylatemonomers, epoxy monomers, oxetane monomers, isocyanate monomers, siliconmonomers, fluorine-based monomers or a copolymer thereof.

The reaction medium may be any medium known to be conventionally used toprepare a synthetic resin, polymer or copolymer without limitation. Forexample, the reaction medium may be distilled water. The chain transferagent which can be added to the reaction solvent may be, but is notlimited to, an alkyl or aryl mercaptan such as n-butyl mercaptan,n-dodecyl mercaptan, tertiary dodecyl mercaptan, isopropyl mercaptan oraryl mercaptan; a halogen compound such as ketone tetrachloride; or anaromatic compound such as an alpha-methylstyrene dimer or analpha-ethylstyrene dimer. The initiator is a polymerization initiator,which may be, but is not limited to, a peroxide such as octanoylperoxide, decanoyl peroxide or lauroyl peroxide, or an azo-basedcompound such as azobisisobutyronitrile orazobis-(2,4-dimethyl)-valeronitrile. The dispersion stabilizer which canbe included in the reaction medium may be, but is not limited to, anorganic distribution agent such as polyvinyl alcohol, polyolefin-maleicacid or cellulose, or an inorganic distribution agent such as tricalciumphosphate.

The first and second resins have already been described above in detail,and thus further description thereof will be omitted. The presentinvention will be described with reference to the following Examples indetail. However, the present invention is not limited to the followingExamples.

Measurement of Surface Energy

According to the Owens-Wendt-Rabel-Kaelble (OWRK) method, surfaceenergies of first resins and second resins were measured using a dropshape analyzer (Kruss, DSA100). More specifically, the first resins andsecond resins were dissolved in a methyl ethyl ketone solvent to have aconcentration of 15 wt %, and then coated on a LCD glass by bar coating.The coated LCD glass was pre-dried in an oven at 60° C. for 2 minutesand then dried at 90° C. for 1 minute. After drying (or curing),deionized water and diiodomethane were dropped 10 times on the coatedsurface at 25° C., respectively, to get an average value of a contactangle, and surface energy was calculated by substituting a numericalvalue into the OWRK method.

Measurement of Melt Viscosity

Melt viscosities of first resins and second resins were measured using aCapillary Rheometer 1501 (Gottfert). More specifically, after acapillary die was attached to a barrel, the first resins and secondresins were put into the barrel by dividing to 3 parts. A shearviscosity (pa*s) according to a shear rate of 100 to 1000 s⁻¹ wasmeasured at a processing temperature of 240° C.

Measurement of Solubility Parameter

While there are some methods of measuring and calculating solubilityparameters, the solubility parameters of first resins and second resinswere calculated at 25° C. using a known method, the Van Krevelen method[refer to Bicerano, J., Prediction of Polymer Properties, third edition,Marcel Dekker Inc., New York (2002), the disclosure of which isincorporated herein by reference in its entirety]. According to the VanKrevelen method, the solubility parameter was calculated using a groupcontribution theory, and defined as the following formula:

${\delta\left( {{solubility}\mspace{14mu}{parameter}} \right)} = {\sqrt{e_{coh}} = \sqrt{\frac{E_{coh}}{V}}}$

In the formula, E_(coh) is a cohesive energy, V is a molar volume, ande_(coh) is a cohesive energy density. The cohesive energy (E_(coh)) isdefined as follows:E _(coh)=10570.9×(⁰χ^(v)−⁰χ)+9072.8×(2×¹χ−¹χ^(v))+1018.2×N _(VKH)

In the formula, ⁰X, ¹X, ⁰X^(v) and ¹X^(v) are connectivity indices, andN_(VKH) is a correlation term. Each variant was calculated withreference to the disclosed literature [Bicerano, J., Prediction ofPolymer Properties, third edition, Marcel Dekker Inc., New York (2002)].

Observation of Feature of Cross-Section

Samples went through a low temperature impact test. Then, fracturesurfaces of the samples were etched using THF vapor, and alayer-separated cross-section was observed using an SEM.

Experiment for Measuring Pencil Hardness

Pencil hardness of samples was measured under a constant load of 500 gusing a pencil hardness tester (Chungbuk Tech). Scratches were made on asurface of the samples by standard pencils (Mitsubishi; grade 6B to 9H)with a fixed angle of 45 degrees, and therefore a change rate of thesurface was observed (ASTM 3363). The values of pencil hardness areaverage values of the results obtained from tests performed 5 times.

Measurement of Molecular Weight Distribution (PDI)

Molecular weight distribution was measured using gel permeationchromatography (GPC) under conditions as follows:

Instrument: 1200 series produced by Agilent Technologies

Column: 2 PLgel mixed Bs produced by Polymer Laboratories

Solvent: THF

Column Temperature: 40° C.

Concentration of Sample: 1 mg/mL, 100 L injection

Standard: Polystyrene (Mp: 3900000, 723000, 316500, 52200, 31400, 7200,3940 or 485)

As an analysis program, ChemStataion provided by Agilent Technologieswas used, and a weight average molecular weight (Mw) and a numberaverage molecular weight (Mn) were measured using gel permeationchromatography (GPC), and the molecular weight distribution was thencalculated from an equation of Mw/Mn.

Example 1

(1) Preparation of First Resin and Second Resin

As a first resin, a first resin-1 (a thermoplastic resin composed of 60wt % methyl methacrylate, 7 wt % acrylonitrile, 10 wt % butadiene and 23wt % styrene) was used. As a second resin, a second resin-1 was preparedas following: 1500 g of distilled water and 4 g of 2% polyvinylalcoholaqueous solution as a dispersing agent were put into a 3-liter reactorand dissolved. Subsequently, 560 g of methyl methacrylate, 240 g ofglycidyl methacrylate, 2.4 g of n-dodecyl mercaptan as a chain transferagent and 2.4 g of azobisisobutyronitrile as an initiator were furtheradded thereto, and mixed while stirring at 400 rpm. The mixture waspolymerized by 3-hour reaction at 60° C., and cooled to 30° C., therebyobtaining a bead-type second resin-1. Afterward, the second resin-1 waswashed three times with distilled water, dehydrated and dried in anoven.

As the results of measurement of the physical properties of the firstresin-1 and the second resin-1, it was shown that a difference insurface energy was 6.4 mN/m, a difference in melt viscosity was 180pa*s, a difference in solubility parameter was 0.5 (J/cm³)^(1/2), aweight average molecular weight of the second resin obtained by GPC was100K, and a molecular weight distribution (PDI) of the second resin was2.1.

(2) Preparation of Resin Blend and Resin Article Using the Same

After 90 parts by weight of the first resin-1 was blended with 10 partsby weight of the second resin-1, the blend was extruded using atwin-screw extruder (Leistritz) at 240° C., thereby obtaining a pellet.A layer separation was observed in the pellet. Then, the pellet wasinjected using an EC100Φ30 injector (ENGEL) at 240° C., therebyobtaining a sample 1 having a thickness of 3200 μm. A pencil hardness ofthe sample 1 was 2H, and layer separation occurred. The feature of thecross-section of the sample 1 observed by using SEM is shown in FIG. 7

Example 2

(1) Preparation of First Resin and Second Resin

As a first resin, the first resin-1 of Example 1 was used. As a secondresin, a second resin-2 was prepared as following: 1500 g of distilledwater and 4 g of 2% polyvinylalcohol aqueous solution as a dispersingagent were put into a 3-liter reactor and dissolved. Subsequently, 760 gof methyl methacrylate, 40 g of perfluorohexylethyl methacrylate, 2.4 gof n-dodecyl mercaptan as a chain transfer agent and 2.4 g ofazobisisobutyronitrile as an initiator were further added thereto, andmixed while stirring at 400 rpm. The mixture was polymerized by 3-hourreaction at 60° C., and cooled to 30° C., thereby obtaining a bead-typesecond resin-2. Afterward, the second resin-2 was washed three timeswith distilled water, dehydrated and dried in an oven.

As a first resin, the first resin-1 of Example 1 was used. As a secondresin, a second resin-2 was prepared as following: 1500 g of distilledwater and 4 g of 2% polyvinylalcohol aqueous solution as a dispersingagent were put into a 3-liter reactor and dissolved. Subsequently, 760 gof methyl methacrylate, 40 g of perfluorohexylethyl methacrylate, 2.4 gof n-dodecyl mercaptan as a chain transfer agent and 2.4 g ofazobisisobutyronitrile as an initiator were further added thereto, andmixed while stirring at 400 rpm. The mixture was polymerized by 3-hourreaction at 60° C., and cooled to 30° C., thereby obtaining a bead-typesecond resin-2. Afterward, the second resin-2 was washed three timeswith distilled water, dehydrated and dried in an oven.

As the results of measurement of the physical properties of the firstresin-1 and the second resin-2, it was shown that a difference insurface energy was 4.2 mN/m, a difference in melt viscosity was 250pa*s, a difference in solubility parameter was 0.2 (J/cm³)^(1/2), aweight average molecular weight of the second resin obtained by GPC was100K, and a molecular weight distribution (PDI) of the second resin was2.0.

(2) Preparation of Resin Blend and Resin Article Using the Same

A sample 2 having a thickness of 3200 μm was prepared by the same methodas Example 1, except that 10 parts by weight of the second resin-2 wasused instead of 10 parts by weight of the second resin-1. A pencilhardness of the sample 2 was 2H, and layer separation occurred.

Example 3

(1) Preparation of First Resin and Second Resin

As a first resin, the first resin-1 of Example 1 was used. As a secondresin, a second resin-3 was prepared by the same method as described inExample 1, except that 560 g of methyl methacrylate, 240 g of tertiarybutyl methacrylate, 2.4 g of n-dodecyl mercaptan as a chain transferagent and 3.2 g of azobisisobutyronitrile as an initiator were put intothe reactor.

As the results of measurement of the physical properties of the firstresin-1 and the second resin-3, it was shown that a difference insurface energy was 1.1 mN/m, a difference in melt viscosity was 360pa*s, a difference in solubility parameter was 0.7 (J/cm³)^(1/2), aweight average molecular weight of the second resin obtained by GPC was80K, and a molecular weight distribution (PDI) of the second resin was1.9.

(2) Preparation of Resin Blend and Resin Article Using the Same

A sample 3 having a thickness of 3200 μm was prepared by the same methodas Example 1, except that 10 parts by weight of the second resin-3 wasused instead of 10 parts by weight of the second resin-1. A pencilhardness of the sample 3 was 2H, and layer separation occurred.

Example 4

(1) Preparation of First Resin and Second Resin

As a first resin, a first resin-2 (a thermoplastic resin composed of 21wt % of acrylonitrile, 15 wt % of butadiene and 64 wt % of styrene) wasused. As a second resin, the second resin-1 of Example 1 was used.

As the results of measurement of the physical properties of the firstresin-2 and the second resin-1, it was shown that a difference insurface energy was 6.1 mN/m, a difference in melt viscosity was 120pa*s, a difference in solubility parameter was 0.7 (J/cm³)^(1/2), aweight average molecular weight of the second resin obtained by GPC was100K, and a molecular weight distribution (PDI) of the second resin was2.1.

(2) Preparation of Resin Blend and Resin Article Using the Same

A sample 4 having a thickness of 3200 μm was prepared by the same methodas described in Example 1, except that 90 parts by weight of the firstresin-2 was used instead of 90 parts by weight of the first resin-1. Apencil hardness of the sample 4 was HB, and layer separation occurred.

Comparative Example 1

Comparative Example 1 was prepared with only the first resin-1 ofExample. Particularly, 100 parts by weight of the first resin-1 ofExample 1 was extruded using a twin-screw extruder (Leistritz) at 240°C., thereby obtaining a pellet. Then, the pellet was injected using anEC100Φ30 injector (ENGEL) at 240° C., thereby obtaining a sample 5having a thickness of 3200 μm.

As the results obtained by measuring physical properties of the sample5, a pencil hardness was F, and layer separation was not observed.

Comparative Example 2

100 parts by weight of the first resin-2 of Example 4 was extruded usinga twin-screw extruder (Leistritz) at 240° C., thereby obtaining apellet. Then, the pellet was injected using an EC100Φ30 injector (ENGEL)at 240° C., thereby obtaining a sample 6 having a thickness of 3200 μm.

As the results obtained by measuring physical properties of the sample6, a pencil hardness was 2B, and layer separation was not observed.

Comparative Example 3

(1) Preparation of First Resin and Second Resin

As a first resin, the first resin-1 of Example 1 was used. As a secondresin, a second resin-4 was prepared as following: 1500 g of distilledwater and 4 g of 2% polyvinylalcohol aqueous solution as a dispersingagent were put into a 3-liter reactor and dissolved. Subsequently, 40 gof methyl methacrylate, 760 g of perfluorohexylethyl methacrylate, 2.4 gof n-dodecyl mercaptan as a chain transfer agent and 2.4 g ofazobisisobutyronitrile as an initiator were further added thereto, andmixed while stirring at 400 rpm. The mixture was polymerized by 3-hourreaction at 60° C., and cooled to 30° C., thereby obtaining a bead-typesecond resin-4. Afterward, the second resin-4 was washed three timeswith distilled water, dehydrated and dried in an oven.

As the results of measurement of the physical properties of the firstresin-1 and the second resin-4, it was shown that a difference insurface energy was 37 mN/m, a difference in melt viscosity was 375 pa*s,a difference in solubility parameter was 3.5 (J/cm³)^(1/2), a weightaverage molecular weight of the second resin measured by GPC was 100K,and a molecular weight distribution (PDI) of the second resin was 2.1.

(2) Preparation of Resin Blend and Resin Article Using the Same

A sample 7 having a thickness of 3200 μm was prepared by the same methodas described in Example 1, except that 10 parts by weight of a secondresin-4 was used instead of 10 parts by weight of the second resin-1. Adetachment between the first resin and the second resin in the sample 7occurred, and thus a pencil hardness was not measured.

Comparative Example 4

(1) Preparation of First Resin and Second Resin

As a first resin, the first resin-1 of Example 1 was used. As a secondresin, a second resin-5 was prepared by the same method as described inExample 1, except that 0.8 g of n-dodecyl mercaptan and 1.6 g ofazobisisobutyronitrile were used instead of 2.4 g of n-dodecyl mercaptanand 2.4 g of azobisisobutyronitrile.

As the results of measurement of the physical properties of the firstresin-1 and the second resin-5, it was shown that a difference insurface energy was 6.3 mN/m, a difference in melt viscosity was 1090pa*s, a difference in solubility parameter was 0.5 (J/cm³)^(1/2), aweight average molecular weight of the second resin obtained by GPC was205K, and a molecular weight distribution (PDI) of the second resin was3.3.

(2) Preparation of Resin Blend and Resin Article Using the Same

A sample 8 having a thickness of 3200 μm was prepared by the same methodas Example 1, except that 10 parts by weight of the second resin-5 wasused instead of 10 parts by weight of the second resin-1. A pencilhardness of the sample 8 was H, layer separation was partially observed,and a thickness of separated layer was non-uniform in parts.

Comparative Example 5

(1) Preparation of First Resin and Second Resin

As a first resin, the first resin-1 of Example 1 was used. As a secondresin, a second resin-6 was prepared by the same method as described inExample 3, except that 4.8 g of n-dodecyl mercaptan and 2.4 g ofazobisisobutyronitrile were used instead of 2.4 g of n-dodecyl mercaptanand 3.2 g of azobisisobutyronitrile.

As the results of measurement of the physical properties of the firstresin-1 and the second resin-6, it was shown that a difference insurface energy was 1 mN/m, a difference in melt viscosity was 610 pa*s,a difference in solubility parameter was 0.7 (J/cm³)^(1/2), a weightaverage molecular weight of the second resin was 42K, and a molecularweight distribution (PDI) of the second resin was 3.2.

(2) Preparation of Resin Blend and Resin Article Using the Same

A sample 9 having a thickness of 3200 μm was prepared by the same methodas described in Example 3, except that 10 parts by weight of a secondresin-6 was used instead of 10 parts by weight of the second resin-3. Apencil hardness of the sample 9 was F, and layer separation was notobserved.

Comparative Example 6

(1) Preparation of First Resin and Second Resin

As a first resin, the first resin-1 of Example 1 was used. As a secondresin, a second resin-7 was prepared by the same method as described inExample 3, except that 0.5 g of n-dodecyl mercaptan and 1.6 g ofazobisisobutyronitrile were used instead of 2.4 g of n-dodecyl mercaptanand 3.2 g of azobisisobutyronitrile.

As the results of measurement of the physical properties of the firstresin-1 and the second resin-7, it was shown that a difference insurface energy was 1 mN/m, a difference in melt viscosity was 1390 pa*s,a difference in solubility parameter was 0.7 (J/cm³)^(1/2), a weightaverage molecular weight of the second resin was 245K, and a molecularweight distribution (PDI) of the second resin was 5.3.

(2) Preparation of Resin Blend and Resin Article Using the Same

A sample 10 having a thickness of 3200 μm was prepared by the samemethod as described in Example 3, except that 10 parts by weight of thesecond resin-7 was used instead of 10 parts by weight of the secondresin-3. A pencil hardness of the sample 10 was F, and layer separationwas not observed.

Comparative Example 7

(1) Preparation of First Resin and Second Resin

As a first resin, the first resin-1 of Example 1 was used. As a secondresin, a second resin-8 was prepared by the same method as described inExample 3, except that 0.4 g of n-dodecyl mercaptan and 1.1 g ofazobisisobutyronitrile were used instead of 2.4 g of n-dodecyl mercaptanand 3.2 g of azobisisobutyronitrile.

As the results of measurement of the physical properties of the firstresin-1 and the second resin-8, it was shown that a difference insurface energy was 1 mN/m, a difference in melt viscosity was 2200 pa*s,a difference in solubility parameter was 0.7 (J/cm³)^(1/2), a weightaverage molecular weight of the second resin was 320K, and a molecularweight distribution (PDI) of the second resin was 5.2.

(2) Preparation of Resin Blend and Resin Article Using the Same

A sample 11 having a thickness of 3200 μm was prepared by the samemethod as described in Example 3, except that 10 parts by weight of thesecond resin-8 was used instead of 10 parts by weight of the secondresin-3. A pencil hardness of the sample 11 was F, and layer separationwas not observed.

As shown in Examples 1-4 and Comparative Examples 1-7, the layerseparation was observed in Examples 1 to 4 using the first resin andsecond resin having the difference in surface energy, melt viscosity orsolubility parameter as described herein. It was further observed thatthe resin article prepared according to the Examples 1 to 4 had a layerformed with the first resin and a layer formed with the second resin.Here, the first resin layer constituted the body of the resin articleand the second resin layer constituted the surface on the body.

As the second resin layer was formed on a surface of the resin articleby the melt processing, the resin article can have improved surfacecharacteristics. More particularly, since the second resin polymerizedfrom a methyl methacrylate-based monomer, as illustrated in Examples 1to 5, could exhibit an excellent anti-scratch characteristic due to ahigh pencil hardness of HB or more, the resin article showed an improvedhardness property. Although the hardness property was illustrated in theExamples 1-5 for the purpose of the description of the presentinvention, it will be obvious to one of skilled in the art that anyother property can be added to the second resin to improve a property ofa resin article.

On the other hand, the resin articles prepared using only the firstresin (Comparative Examples 1 and 2) did not have separated layers andhad low surface pencil hardness. Accordingly, to use the resin articleobtained in Comparative Examples 1 and 2 for a part of an automobile ora part of an electric device, a coating process was needed to improve asurface characteristic.

Meanwhile, it was understood from Examples 1 to 4 that layer separationoccurred in the resin article only when the first resin and the secondresin had a certain difference in melt viscosity (at a shear rate of 100to 1000 s⁻¹ and at a processing temperature of the resin blend).

In addition, it was understood from Comparative Examples 4 to 7 that thelayer separation was observed only when the second resin had weightaverage molecular weight and molecular weight distribution as describedthe above.

While the invention has been shown and described with reference tocertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the scope of the invention as defined bythe appended claims.

What is claimed is:
 1. A pellet, comprising: a core including a firstresin; and a shell including a second resin having a molecular weightdistribution of 1 to 2.5 and a difference in melt viscosity from thefirst resin of 0.1 to 3000 pa*s at a shear rate of 100 to 1000 s⁻¹ and aprocessing temperature of the pellet.